Before a semiconductor wafer is patterned (or in a pre-process), the wafer has a constant thickness in order to make the handling thereof easy. On the other hand, after the patterning of the wafer (or in a post-process), the wafer is subjected to the step of grinding the rear surface of the wafer mechanically so as to thin the wafer into a given thickness and further the step of cutting the thinned wafer into chips. Generally, in this post-process, the semiconductor wafer is subjected to the respective working-steps in the state that a pressure-sensitive adhesive sheet is adhered to (or laminated on) the wafer in order to protect the patterned surface of the wafer in the wafer-thinning step or fix and support the thinned wafer in the step of cutting the thinned wafer. In particular, in the case that the semiconductor wafer is worked to be thin and subsequently the rear surface of the wafer is subjected to etching treatment or sputtering or vapor-depositing treatment or in the case that a die bond film is adhered to the wafer, the wafer is heated to a temperature of about 100 to 200° C. in the state that the a protective sheet is adhered to the wafer.
In recent years, the tendency that semiconductor wafers are made large-sized or made thin for the use thereof as IC cards or others has been advancing. However, the semiconductor wafers made large-sized or thin are largely warped by heat in the wafer-thinning step or in a heating environment, so that the wafers may easily be damaged. Consequently, there are caused problems such that the semiconductor wafers cannot be put into carrying cassettes; the wafers are cracked when they are carried or adhesive sheets are peeled therefrom; and the patterned surfaces thereof are damaged (see Japanese Patent Application Laid-Open (JP-A) Nos. 6-322338 and 2000-355678).